The invention relates to an internal combustion engine with at least two camshafts arranged next to one another and each having a device for rotary angle adjustment with respect to a crankshaft, and it can be implemented particularly advantageously on internal combustion engines having in each case an overhead inlet and outlet camshaft.
EP 1 046 793 A2 discloses a generic internal combustion engine with two camshafts arranged next to one another and in each case produced with a device for rotary angle adjustment with respect to a crankshaft. In that internal combustion engine, the devices for rotary angle adjustment are fastened at the drive-side ends of the two camshafts. Those ends are each mounted in a radial bearing in the cylinder head of the internal combustion engine, in principle providing hydraulic actuating drives. Within each device there are a plurality of hydraulic pressure chambers which act in relation to one another in pairs. When the chambers are acted upon alternately or simultaneously by a hydraulic pressure medium, this causes a rotary angle adjustment of the respective camshaft with respect to the crankshaft of the internal combustion engine. Supply and discharge of hydraulic pressure medium to and from the pressure chambers of each device take place in this case via the radial bearings of the camshafts and they are controlled separately by two electromagnetic hydraulic valves. Each valve consists essentially of an electromagnet and of a hollow-cylindrical valve housing connected to the latter. These valve housings can be plugged into a valve receptacle on the cylinder head of the internal combustion engine. On their circumference the housings the housings have a plurality of annular grooves which are spaced axially from one another. Into each groove are incorporated a plurality of radial orifices which issue into the interior of the valve housing. Furthermore, the valve housings are open on their free end faces, so that the hydraulic valves are fluidically connected via the annular grooves on their valve housings to the radial bearings of the camshafts and to a pressure connection and via the valve housings open on the end faces to a tank connection.
This known internal combustion engine has the disadvantage, however, that the valve receptacles for the hydraulic valves are integrated as an additional middle socket in a one-part bearing bridge produced as part of the radial bearings of the two camshafts. The pressure medium ducts are additionally arranged in a highly complicated way, for connecting the valve receptacles to the radial bearings of the two camshafts. Those ducts have to be drilled or otherwise introduced into this bearing bridge, in order to avoid overlaps of these pressure medium ducts with one another and with the pressure medium ducts, as the latter ducts are likewise arranged in a highly complicated manner in the cylinder head of the internal combustion engine, for the pressure connection and for the tank connection of the hydraulic valves. These complicated pressure medium ducts in the cylinder head of the internal combustion engine and in the bearing bridge of the camshaft radial bearings require a relatively high outlay in manufacturing terms. Together with the highly material-intensive bearing bridge, the above described ducts adversely increases the production costs for the internal combustion engine.
Other hydraulic valves having valve housings which, in a way similar to the hydraulic valve disclosed in EP 1 138 939 A1, have no annular grooves on the circumference. Instead, one-sided radial orifices are arranged offset to one another. This is admittedly a conceivable simpler arrangement of the necessary pressure medium ducts in the cylinder head and between the radial bearings of the camshafts and the valve receptacles. But, factors likewise increasing the production costs of the internal combustion engine would have to be taken into account for the necessary change in the hydraulic concept of the devices for rotary angle adjustment and for the production or procurement of the modified hydraulic valves.
The object of the invention is, therefore, to provide an internal combustion engine with at least two camshafts arranged next to one another. Each camshaft has a device for rotary angle adjustment with respect to a crankshaft. The engine is designed with simple valve receptacles, which are capable of being produced cost-effectively. These receptacles are provided for the electromagnetic hydraulic valves of the device for rotary angle adjustment and, when conventional hydraulic valves with annular grooves in the valve housing are used, the receptacles make it possible to have a simplified arrangement and manufacture of the pressure medium ducts in the cylinder head and between the radial bearings of the camshafts and the valve receptacles.
The invention concerns an internal combustion engine with two camshafts arranged next to each other and also having a device for rotary angle adjustment with respect to an engine crankshaft. The object is achieved by the valve receptacles of the hydraulic valves being passage bores which are incorporated directly next to one another, and arranged vertically, into a cylinder head cover of the internal combustion engine between the camshafts. The bores have a larger diameter than the valve housings of the hydraulic valves. The bores are fluidically connected, via horizontal transverse ducts on the underside of the cylinder head cover and via vertical riser ducts in the bore walls of the valve receptacles, to the radial bearings of the camshafts and to the pressure connection of the hydraulic valves. The separation of the individual fluid streams to the hydraulic valves and to and from the radial bearings of the camshafts takes place in each case via an adapter sleeve which is plugged axially onto each valve housing. This seals off relative to one another the annular grooves in the valve housings and the riser ducts in the bore walls of the valve receptacles. The diameters of the ducts correspond in each case to the inside diameter of the valve receptacles. Each duct has a radial bore assigned to each riser duct level with the annular grooves in the valve housing in the bore walls of the valve receptacles.
In an advantageous embodiment of the internal combustion engine according to the invention, the valve housings of the hydraulic valves and the plugged-on adapter sleeves are in this case connected nonpositively to one another and are secured against rotation relative to one another preferably by a press fit between the outside diameter of the valve housings and the inside diameter of the adapter sleeves. Such securing against rotation proved necessary, since the actual pressure medium distribution of the hydraulic valves in this case takes place via the radial bores in the adapter sleeves. The radial bores are aligned exactly with the riser ducts in the bore walls of the valve receptacles. By means of a press connection between the adapter sleeves and the valve housings, in conjunction with an exactly positioned screw connection of the hydraulic valves on the cylinder head cover of the internal combustion engine, unintentional rotation of the adapter sleeves with respect to the riser ducts in the bore walls of the valve receptacles can be avoided. It would also be conceivable in this respect, however, to insert the adapter sleeves, exactly aligned by means of a press fit, into the passage bores for the valve receptacles and to fasten the hydraulic valves plugged into the adapter sleeves on the cylinder head cover of the internal combustion engine by means of a screw connection positioned in any desired way.
Instead of a nonpositive connection, in an alternative embodiment of the internal combustion engine designed according to the invention, it is also possible to connect the valve housings of the hydraulic valves and the plugged-on adapter sleeves to one another by a positive connection and, in cooperation with an exactly positioned screw connection of the hydraulic valves on the cylinder head cover of the internal combustion engine, to secure them against rotation relative to one another. In this case, it proved particularly cost-effective to connect the adapter sleeves to the valve housing by caulking the lower sleeve end face together with the lower edge portion of each valve housing. It would also be conceivable to retain the adapter sleeves on the valve housings in each case by means of a securing ring attached onto the end of the valve housings and to secure the adapter sleeves against rotation by means of a radial bore in the adapter sleeve and an inserted cylindrical pin.
A further feature of the internal combustion engine according to the invention is that the vertical transverse ducts on the underside of the cylinder head cover are made open toward the cylinder head. During the mounting of the cylinder head cover on the cylinder head, the ducts can be closed relative to one another in a fluid-tight manner by a planar cylinder head countersurface. By virtue of the valve receptacles being designed and arranged according to the invention, these transverse ducts, and also the riser ducts in the bore walls of the valve receptacles, can be designed as rectilinearly running pressure medium ducts with semicircular or angular cross sections and can thus be produced relatively simply and cost-effectively during the casting of the cylinder head cover. In this case, advantageously, at the same time the pressure connection of the hydraulic valves is arranged in the cylinder head countersurface, closing the transverse ducts. That connection is in the form of a pressure medium duct which leads to a pressure medium pump and the fluid stream of which is subdivided in the cylinder head cover, via two separate vertical transverse ducts, into two part streams and is transferred to the respective riser duct to the hydraulic valves. However, such a separation of the fluid stream of an individual pressure connection for two hydraulic valves is also possible elsewhere in the cylinder head of the internal combustion engine or may even be dispensed with completely when the two hydraulic valves are connected to separate pressure connections.
Furthermnore, in a further expedient embodiment of the internal combustion engine designed according to the invention, the planar cylinder head countersurface of the cylinder head cover is also utilized for the discharge of pressure medium from the devices for rotary angle adjustment via the hydraulic valves, in order, in this case too, to avoid a complicated arrangement and manufacture of the necessary pressure medium ducts. This takes place in that the passage bores designed in the cylinder head cover as valve receptacles are continued in the cylinder head countersurface as axially parallel outflow bores which have the same diameter as the valve receptacles and which lead to a pressure medium passage of the internal combustion engine and can likewise be produced relatively simply and cost-effectively during the casting of the cylinder head.
Finally, as the last feature of the internal combustion engine designed according to the invention, it is also proposed to make the axial length of the adapter sleeves plugged onto the valve housings of the hydraulic valves slightly greater than the depth of the passage bores for the valve receptacles in the cylinder head cover, in order to avoid adverse pressure medium leakages during the transition of the discharged pressure medium out of the hydraulic valves into the cylinder head of the internal combustion engine. What is achieved by the greater length of the adapter sleeves is that the hydraulic valves plugged into the valve receptacles project with their adapter sleeves slightly into the outflow bores in the cylinder head countersurface, so that the discharged pressure medium is transferred completely and cannot flow out in an uncontrolled manner between the cylinder head cover and the cylinder head.
Thus, the internal combustion engine designed according to the invention, with at least two camshafts arranged next to one another and in each case produced with a device for rotary angle adjustment with respect to a crankshaft, has the advantage, as compared with the internal combustion engines known from the prior art, that it has very simple valve receptacles, capable of being produced cost-effectively, for the electromagnetic hydraulic valves of the device for rotary angle adjustment in the form of passage bores incorporated directly into a cylinder head cover. By likewise very simply designed adapter sleeves being plugged onto the valve housings of the hydraulic valves, it is possible in this case both to use conventional hydraulic valves with annular grooves in the valve housing and at the same time to have a simplified arrangement and design of the pressure medium ducts for connecting the valve receptacles to the radial bearings of the camshafts in the form of transverse and riser ducts, open on one side, on the underside of the cylinder head cover and in the bore walls of the valve receptacles. At the same time, the valve receptacles in the cylinder head cover and the adapter sleeves on the valve housings allow an advantageous arrangement of the pressure and tank connections for the hydraulic valves in the cylinder head of the internal combustion engine, so that, overall, a reduction in the outlay in manufacturing terms and a lowering of the production costs of the internal combustion engine designed according to the invention are achieved.